cheradenine

If I run a SA for 2023-24, with a salary of 37,500, Interest of 2,000 and dividends of 1,000, the calculation produces this, which is what I expected : Amount Percentage Total Pay, pensions, profit etc. (UK rate for England and Northern Ireland) Basic rate £ 24,930.00 × 20% £4,986.00 Savings interest from banks or building societies, securities etc. Basic rate band at nil rate £1000.00 × 0% £0.00 Basic rate £1,000 x 20% £200.00 Income Tax charged after allowances and reliefs £5,186.00 However, if I adjust the interest to 15,000 (still with a salary of 37,500 and dividends of 1,000, the calculation produces this: Amount Percentage Total Pay, pensions, profit etc. (UK rate for England and Northern Ireland) Basic rate £ 37,500.00 × 20% £7,500.00 Savings interest from banks or building societies, securities etc. Basic rate band at nil rate £200.00 × 0% £0.00 Higher rate band at nil rate £300.00 × 0% £0.00 Higher rate £1,930.00 × 40% £772.00 Income Tax charged after allowances and reliefs £8,272.00 Is there some detail as to how the calculation works, as I don't understand why there is 37,500 now attributed to "Pay", when the amount after personal allowance is £24,930 (just as it is in the first example), and why the nil rate has been spread across two bands and not wholly in the lower rate band. I.E: I was expecting Amount Percentage Total Pay, pensions, profit etc. (UK rate for England and Northern Ireland) Basic rate £ 24,930.00 × 20% £4,986.00 Savings interest from banks or building societies, securities etc. Basic rate band at nil rate £500.00 × 0% £0.00 Basic rate £12,270 x 20% £2454.00 Higher rate £2,230 × 40% £892.00 Income Tax charged after allowances and reliefs £8,272.00 In fact, if I do 37500/12770/1000 (employment, interest, dividend), it reports 24,930 as basic rate in "pay, pensions, profit", but a single pound more (37500/12771/1000) and it changes to 37,201 ?!?